Buggy code:
public class ClasspathEntry implements IClasspathEntry { public static final String TAG_CLASSPATH = "classpath" ; public static final String TAG_CLASSPATHENTRY = "classpathentry" ; public static final String TAG_OUTPUT = "output" ; public static final String TAG_KIND = "kind" ; public static final String TAG_PATH = "path" ; public static final String TAG_SOURCEPATH = "sourcepath" ; public static final String TAG_ROOTPATH = "rootpath" ; public static final String TAG_EXPORTED = "exported" ; public static final String TAG_INCLUDING = "including" ; public static final String TAG_EXCLUDING = "excluding" ; public static final String TAG_ATTRIBUTES = "attributes" ; public static final String TAG_ATTRIBUTE = "attribute" ; public static final String TAG_ATTRIBUTE_NAME = "name" ; public static final String TAG_ATTRIBUTE_VALUE = "value" ; public static final String TAG_COMBINE_ACCESS_RULES = "combineaccessrules" ; public static final String TAG_ACCESS_RULES = "accessrules" ; public static final String TAG_ACCESS_RULE = "accessrule" ; public static final String TAG_PATTERN = "pattern" ; public static final String TAG_ACCESSIBLE = "accessible" ; public static final String TAG_NON_ACCESSIBLE = "nonaccessible" ; public static final String TAG_DISCOURAGED = "discouraged" ; public int entryKind ; public int contentKind ; public IPath path ; private IPath [ ] inclusionPatterns ; private char [ ] [ ] fullInclusionPatternChars ; private IPath [ ] exclusionPatterns ; private char [ ] [ ] fullExclusionPatternChars ; private static final char [ ] [ ] UNINIT_PATTERNS = new char [ ] [ ] { "Non-initialized<seq2seq4repair_space>yet" . toCharArray ( ) } ; private boolean combineAccessRules ; private String rootID ; private AccessRuleSet accessRuleSet ; public static final IPath [ ] INCLUDE_ALL = new IPath [ ] { } ; public static final IPath [ ] EXCLUDE_NONE = new IPath [ ] { } ; public static final IClasspathAttribute [ ] NO_EXTRA_ATTRIBUTES = new IClasspathAttribute [ ] { } ; public static final IAccessRule [ ] NO_ACCESS_RULES = new IAccessRule [ ] { } ; public IPath sourceAttachmentPath ; public IPath sourceAttachmentRootPath ; public IPath specificOutputLocation ; public static final int K_OUTPUT = 10 ; public boolean isExported ; private IClasspathAttribute [ ] extraAttributes ; public ClasspathEntry ( int contentKind , int entryKind , IPath path , IPath [ ] inclusionPatterns , IPath [ ] exclusionPatterns , IPath sourceAttachmentPath , IPath sourceAttachmentRootPath , IPath specificOutputLocation , boolean isExported , IAccessRule [ ] accessRules , boolean combineAccessRules , IClasspathAttribute [ ] extraAttributes ) { } private static AccessRuleSet createAccessRuleSet ( IAccessRule [ ] accessRules ) { } public boolean combineAccessRules ( ) { } public ClasspathEntry combineWith ( ClasspathEntry referringEntry ) { } private IAccessRule [ ] combine ( IAccessRule [ ] referringRules , IAccessRule [ ] rules , boolean combine ) { if ( ! combine ) return rules ; <START_BUG> if ( rules == null ) <END_BUG> return referringRules ; int referringRulesLength = referringRules . length ; int accessRulesLength = rules . length ; int rulesLength = referringRulesLength + accessRulesLength ; IAccessRule [ ] result = new IAccessRule [ rulesLength ] ; System . arraycopy ( referringRules , 0 , result , 0 , referringRulesLength ) ; System . arraycopy ( rules , 0 , result , referringRulesLength , accessRulesLength ) ; return result ; } private static IClasspathAttribute [ ] decodeExtraAttributes ( Element element ) { } private static IAccessRule [ ] decodeAccessRules ( Element element ) { } private static IPath [ ] decodePatterns ( Element element , String tag ) { } public char [ ] [ ] fullExclusionPatternChars ( ) { } public char [ ] [ ] fullInclusionPatternChars ( ) { } public void elementEncode ( XMLWriter writer , IPath projectPath , boolean indent , boolean newLine ) { } private void encodeExtraAttributes ( XMLWriter writer , boolean indent , boolean newLine ) { } private void encodeAccessRules ( XMLWriter writer , boolean indent , boolean newLine ) { } private void encodeAccessRule ( AccessRule accessRule , XMLWriter writer , boolean indent , boolean newLine ) { } public static IClasspathEntry elementDecode ( Element element , IJavaProject project ) { } private static void encodePatterns ( IPath [ ] patterns , String tag , Map parameters ) { } public boolean equals ( Object object ) { } private static boolean equalAttributes ( IClasspathAttribute [ ] firstAttributes , IClasspathAttribute [ ] secondAttributes ) { } private static boolean equalPatterns ( IPath [ ] firstPatterns , IPath [ ] secondPatterns ) { } public IAccessRule [ ] getAccessRules ( ) { } public AccessRuleSet getAccessRuleSet ( ) { } public int getContentKind ( ) { } public int getEntryKind ( ) { } public IPath [ ] getExclusionPatterns ( ) { } public IClasspathAttribute [ ] getExtraAttributes ( ) { } private String getMessageTemplate ( ) { } public IPath [ ] getInclusionPatterns ( ) { } public IPath getOutputLocation ( ) { } public IPath getPath ( ) { } public IPath getSourceAttachmentPath ( ) { } public IPath getSourceAttachmentRootPath ( ) { } public int hashCode ( ) { } public boolean isExported ( ) { } static int kindFromString ( String kindStr ) { } static String kindToString ( int kind ) { } public static IAccessRule [ ] getAccessRules ( IPath [ ] accessibleFiles , IPath [ ] nonAccessibleFiles ) { } public String toString ( ) { } public String rootID ( ) { } public IClasspathEntry getResolvedEntry ( ) { } public static IJavaModelStatus validateClasspath ( IJavaProject javaProject , IClasspathEntry [ ] rawClasspath , IPath projectOutputLocation ) { } public static IJavaModelStatus validateClasspathEntry ( IJavaProject project , IClasspathEntry entry , boolean checkSourceAttachment , boolean recurseInContainers ) { } }

Fix:
if ( ( rules == null ) || ( ( rules . length ) == 0 ) )